Motor vehicles are equipped with a windshield wiper device for cleaning or wiping a surface of a windshield. The windshield wiper device includes a wiper motor, a wiper arm and a wiper blade. The wiper arm is connected to a rotating shaft of the wiper motor at its base end and is oscillated by the wiper motor. The wiper blade is separably joined to a distal end of the wiper arm. The wiper blade is positioned on the surface of the windshield by the wiper arm. The wiper blade wipes the surface of the windshield while sliding thereon through oscillating movements of the wiper arm.
The wiper blade has an elongated wiper strip and a frame for holding and supporting the wiper strip in its longitudinal direction. The wiper strip is placed in contact with the windshield surface. The frame may comprise an assembly including a main yoke and a plurality of sub yokes linked to the main yoke. A wiper blade with such a frame is known in the art as “a conventional wiper blade.” A wiper blade, which uses a single frame curving with a certain curvature and having a thin and elongated bar shape as the frame, has been recently used. Such a wiper blade is known in the art as “a flat wiper blade” or “a flat-bar wiper blade.” The flat wiper blade has a height lower than a conventional wiper blade and is subjected to less air resistance when compared to the conventional wiper blade. Further, the flat wiper blade can bring its wiper strip into contact the windshield surface under a uniform load.
When such wiper blades are placed on a windshield of a vehicle, wind or air stream impinging on the windshield during running of a vehicle exerts forces to the wiper blade throughout the entire length of the wiper blade. The wiper blade is positioned generally vertically on the surface of the inclined windshield. Thus, the forces caused by the wind or air stream act in a direction of lifting up the wiper blade from the surface of the windshield. The faster the vehicle runs, the stronger such lift forces would be. This weakens the contact between the wiper strip and the windshield surface, thus deteriorating wiping performance.
To address the deterioration of the wiping performance due to the lift of a wiper blade, a main yoke and sub yokes of a convention wiper blade are provided with apertures permitting the air stream to pass therethrough. Further, to apply forces in a direction opposite to the lift of the wiper blade during running of a vehicle to restrain the lift, spoilers are attached to a wiper blade. The spoiler has a profile that produces reaction forces toward the windshield surface from reaction to the wind or air stream.
Such a spoiler is made from a plastic or rubber material. The spoiler may be separably attached to the main yoke of a conventional wiper blade. Further, the spoiler may be separably attached to the frame of a flat wiper blade. By way of example of a coupling configuration between a spoiler and a flat wiper blade, U.S. Pat. No. 7,228,588 discloses that a frame and spoilers of the flat wiper blade are coupled to one another by fitting.